TERES MINOR 367 



horizontal position. When the clavicular and acromial parts act, the arm is raised and flexed 

 (brought forward toward the chest). When the acromial and spinous parts act, the arm is 

 raised and extended (carried toward the back), but in this instance the arm is not brought to a 

 level with the shoulder-joint, but only about 45" from the hanging position. The inferior part 

 of the serratus anterior and the trapezius act in conjunction with the deltoid in abduction. 

 Abduction is greatest when the arm is rotated lateralward. The ventral portion rotates the 

 arm medially, the dorsal portion laterally. When the arm is fixed, the deltoid tends to carry 

 the inferior angle of the scapula toward the spinal column and away from the thorax. 



Relatio7is.— On its ventral border the deltoid is in contact with the pectoralis major muscle. 

 Near the clavicle the cephahc vein and a small artery pass between the two muscles. Its dorsal 

 border is continued into a dense fascial sheet which overlies the infraspinatus muscle. Its 

 tendon of insertion passes between the biceps and triceps muscles. The deltoid overhes the 

 coracoid process and upper extremity of the humerus, the coraco-clavicular and coraco-acromial 

 ligaments, and the insertions of the supraspinatus, infraspinatus, and teres minor muscles, the 

 origins of the biceps and coraco-brachiahs, and a part of the long and lateral heads of the triceps. 

 Beneath it run the posterior circumflex arterj^ and axillary (circumflex) nerve. 



Variations. — The clavicular portion is frequently separate from the rest of the muscle. The 

 three portions may be distinctly separate — a condition normal in some of the lower mammals. 

 The clavicular and acromial portions have been found missing. The deep portion of the muscle 

 may be separated as a distinct layer and inserted either into the capsule of the joint or into the 

 humerus. Accessory fasciculi may pass into the muscle from the fascia over the infraspinatus 

 and from the vertebral and axillary borders of the scapula. Not infrequently fasciculi are con- 

 tinued into the muscle from the trapezius — a condition normal in animals with ill-developed 

 clavicles. An accessory tendon of insertion may extend to the radial side of the forearm. 

 Bundles of fibres from the axillary border of the scapula have been seen to cross the deep surface 

 of the deltoid and be inserted into the deltoid fascia. The deltoid may be fused with neighbour- 

 ing muscles, the pectoralis major, trapezius, infraspinatus, brachiahs, brachio-radialis. 



The teres minor (fig. 363). — Origin. — From the upper two-thirds of the axillary border of 

 the infraspinous fossa, and from the septa lying between it and the infraspinatus on the one 

 side and the teres major and subscapularis on the other. The origin is in part fleshy, in part 

 from an aponeurotic band on its ventral surface toward the subscapularis muscle. 



Structure and iiisertion.— The fibre-bundles from this origin take a sUghtly converging course 

 toward a tendon of insertion which extends for some distance on the dorsal surface of the 

 muscle. The muscle is adherent to the capsule of the joint, and terminates on the inferior of 

 the three facets of the great tubercle of the humerus and the postero-lateral aspect of that 

 bone for two or three centimetres below the facet. 



Nerve-supply. — From a branch of the axillary (circumflex) nerve which enters the muscle on 

 its lateral margin about midway between its extremities. A 'ganglion' is usually found upon 

 this nerve. A branch from the nerve to the teres major has also been reported. The nerve 

 fibres are derived from the fifth cervical nerve. 



Action. — 1( acts conjointly with the infraspinatus to rotate the arm lateraU^^ It is a 

 flexor when the arm is down and an extensor when it is abducted. It is also an adductor. 



Relations. — The muscle is in part covered by the deltoid. Ventrally it enters into relations 

 with the long head of the triceps, the teres major, and the subscapularis. Superiorly, the cir- 

 cumflex (dorsal) scapular vessels run between it and the axillary border of the scapula. 



Fig. 357. A and B. — Transverse Sections through the Left Shoulder in the Regions 



INDICATED in THE DIAGRAM. 



In the neighbourhood of the brachial plexus in each section some of the adipose and lymphatic 

 tissue has been removed. In section B the fascia covering the apex of the axillary fossa 

 is thus revealed from above, a and b in the diagram indicate the regions through which 

 pass sections A and B, fig. 351 (p. 352); a' and b', the regions through which pass 

 sections A and B, fig. 362 (p. 375). 



1. Aorta. 2. Arteria brachiahs. 3. A. circumflexa scapulse (dorsaUs scapulse). 4. A. carotis 

 communis. 5. A. mammaria interna. 6. A. subclavia. 7. A. thoracahs laterahs (long 

 thoracic). 8. Costa I. 9. Costa II. 10. Costa III. 11. Costa IV. 12. Costa V. 

 13. Costa VI. 14. Clavicle. 15. Fibrocartilago intervertebrahs (intervertebral disc). 

 16. Fascia axillaris. 17. Fascia cervicalis (superficial layer). 18. Middle layer. 19. F. 

 coraco-clavicularis. 20. F. lumbo-dorsahs. 21. Fascia of posterior serrati. 22. Humerus. 

 23. Medulla spinalis (spinal cord). 24. Musculus biceps — a, long head; b, short head; 

 c, tendon of short head. 25. M. coraco-brachialis. 26. M. deltoideus. 27. M. infraspin- 

 atus. 28.M.iho-costahsdorsi(accessorius). 29.M.intercostalesexterni. 30.M.intercostales 

 interni. 31. M. latissimus dorsi, tendon. 32. M. levator costa?. 33. M. longissimus dorsi. 

 34. M. longus colh. 35. M. pectorahs major. 36. M. pectorahs minor. 37. M. platj-sma. 

 38. M. rhomboideus major. 39. M. scalenus anterior. 40a. M. serratus anterior. 406, 

 M. serratus posterior superior. 41. M. sterno-mastoideus. 42. M. cleido-mastoideus. 

 insertion. 43. M. sterno-hyoideus. 44. M. sterno-thyreoideus. 45. M. subclavius. 46. 

 M. subscapularis. 47. M. teres major. 48. M. teres minor. 49. M. trapezius. 50. 

 M. transverso-spinales. 51. M. triceps — a, long head; b, lateral head. 52. Nervus axillaris 

 53. N. cutaneus antebrachii medialis (internal cutaneous). 54. a-e, Nn. intercostales 

 I-V. 55. N. medianus. 56. N. phrenicus. 57. N. musculocutaneus. 58. N. radialis 

 (musculo-spiral). 59. N. recurrens. 60. N. subscapularis. 61. Sympathetic trunk. 

 62. N. thoracalis anterior. 63. N. thoracahs longus. 64. N. thoracodorsahs (long 

 subscapular). 65. N. ulnaris. 66. N. vagus. 67. CEsophagus. 68. Plexus brachiahs— 

 a, lateral fasciculus; b, medial; c, posterior. 69. Scapula. 70. Sternum. 71. Trachea. 

 72. Venae brachiales. 73. V. cephaUca. 74. V. jugularis anterior. 75. V. jugularis 

 inferior. 76. V. subclavia. 77. Vertebra I. 78. Vertebra II. 79. Vertebra III. 80. 

 Vertebra IV. 81. Vertebra V. 82. Vertebra VI. 



